NEW HAVEN >> Medicare is spending $447 million a year on a controversial cancer-screening test that may not prevent deaths, according to a study at Yale University.

PSA tests — PSA stands for prostate-specific antigen — to detect prostate cancer are not recommended for any man by the U.S. Preventative Services Task Force, which in 2012 stated, “There is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits.”

For men over 75, the benefit is even smaller, because few of them will die of the slow-growing tumor in their prostate glands. And yet, researchers at the Yale Cancer Outcomes, Public Policy and Effectiveness Research Center, found that Medicare, the federally sponsored health care plan for those 65 and older, was spending $145 million on the oldest men, almost a third of its total spending on PSA screenings.

“There is more of a consensus that screening for prostate cancer is unlikely to be beneficial, particularly over the age of 75,” said Dr. Cary Gross, professor at the Yale School of Medicine and director of the Yale COPPER Center.

A positive test may mean a biopsy of the prostate, which carries its own risks. While PSA tests have been debated for several years, “We felt the one thing that was missing from the conversation was how much the Medicare program was spending on it,” Gross said.

The amount spent on a possibly useless test wasn’t the only finding from the study, published in today’s issue of the journal Cancer. Researchers also discovered that there was more than a “threefold variation across geographic regions” in the amount spent, from $17 to $62 per patient, mostly because of follow-up tests. Also, doctors in the areas where Medicare was paying more “were finding more early-stage cancers but not finding less late-stage cancers,” Gross said.

Greater New Haven ranks between the top 25th and 50th percentiles of spending for prostate cancer screening among these Medicare beneficiaries, Gross said.

The finding about variations in spending raises questions about the test as well, because not all early-stage cancers grow into late-state metastatic cancers. Finding more early cancers “doesn’t alone tell me” that cancer deaths will decrease, Gross said.

“This suggests that spending more money on prostate cancer screenings may not necessarily reduce the likelihood of developing metastatic prostate cancer,” he said.

Cancer of the prostate, the gland that produces the fluid in semen, is the second-leading cause of death among men, after lung cancer, according to the American Cancer Society. This year, more than 230,000 new cases will be diagnosed and almost 30,000 will die from the disease.

But the cancer society also states on its website, “Prostate cancer can be a serious disease, but most men diagnosed with prostate cancer do not die from it. In fact, more than 2.5 million men in the United States who have been diagnosed with prostate cancer at some point are still alive today.”

One conclusion, according to Gross is that “we still don’t know how to best target our screening efforts. Why not invest some of that money in conducting more research?” Gross said. “The problem is we are detecting cancers that are often not likely to go on and create health problems.”

“If Medicare’s spending $450 million per year on screening and the best strategy for screening is unclear ... we need to have a concerted effort to advise men about the limitations to prostate cancer screening and to generate more evidence to guide our screening strategies,” Gross said.

Earlier this year, the COPPER Center reported that “in women over 75, there is no evidence whether or not the screenings are effective in bringing about better outcomes,” Gross said in a Register article in January.

Medicare pays more than $1 billion per year for breast cancer screenings, $400 million on women over 75.

The lead author of the latest study is Xiaomei Ma, associate professor at the Yale School of Public Health.

Call Senior Writer Ed Stannard at 203-789-5743.

Correction: This story was edited to clarify what Dr. Cary Gross said about breast cancer screenings. He did not say they were ineffective but that there was no evidence to prove their effectiveness.